LDP hello i keepalive

[mx_krzak]

Jaka jest różnica miedzy tymi dwoma? LDP hello służy do discovery peerów natomiast keepalive do podtrzymywania sesji tcp między peerami. W jednym i drugim jest jakiś holdtime po którym sesja pada. Odnoszę wrażenie jakby ten keepalive był nadmiarowy. Czy nie wystarczyłby tylko hello? Licznik holdtime dla sesji mógłby resetować przecież równie dobrze hello.

[Seba]

Ktos zdefiniowal standard i tak juz jest. Hello i Keepalive robia troche inne rzeczy. Szczegoly:

2.5.5. Maintaining Hello Adjacencies

An LDP session with a peer has one or more Hello adjacencies.

An LDP session has multiple Hello adjacencies when a pair of LSRs is
connected by multiple links that share the same label space; for
example, multiple PPP links between a pair of routers. In this
situation the Hellos an LSR sends on each such link carry the same
LDP Identifier.

LDP includes mechanisms to monitor the necessity of an LDP session
and its Hello adjacencies.

LDP uses the regular receipt of LDP Discovery Hellos to indicate a
peer's intent to use the label space identified by the Hello. An LSR
maintains a hold timer with each Hello adjacency which it restarts
when it receives a Hello that matches the adjacency. If the timer
expires without receipt of a matching Hello from the peer, LDP
concludes that the peer no longer wishes to label switch using that
label space for that link (or target, in the case of Targeted Hellos)
or that the peer has failed. The LSR then deletes the Hello
adjacency. When the last Hello adjacency for a LDP session is
deleted, the LSR terminates the LDP session by sending a Notification
message and closing the transport connection.

2.5.6. Maintaining LDP Sessions

LDP includes mechanisms to monitor the integrity of the LDP session.

LDP uses the regular receipt of LDP PDUs on the session transport
connection to monitor the integrity of the session. An LSR maintains
a KeepAlive timer for each peer session which it resets whenever it
receives an LDP PDU from the session peer. If the KeepAlive timer
expires without receipt of an LDP PDU from the peer the LSR concludes
that the transport connection is bad or that the peer has failed, and
it terminates the LDP session by closing the transport connection.

After an LDP session has been established, an LSR must arrange that
its peer receive an LDP PDU from it at least every KeepAlive time
period to ensure the peer restarts the session KeepAlive timer. The
LSR may send any protocol message to meet this requirement. In
circumstances where an LSR has no other information to communicate to
its peer, it sends a KeepAlive message.

An LSR may choose to terminate an LDP session with a peer at any
time. Should it choose to do so, it informs the peer with a Shutdown
message.

Cytat pochodzi z RFC3036 LDP Specification,

[mx_krzak]

Ktos zdefiniowal standard i tak juz jest. Hello i Keepalive robia troche inne rzeczy.

OK. Czyli trzeba przyjąć, zapamiętać i nie dyskutować

[Seba]

No tak to niestety, albo stety bywa... W sumie w jakims celu te standardy, protokoly sa stworzone i unormowane, i pewne rzeczy trzeba przyjmowac "bez szemrania".
Gdyby byl na forum ktos kto bral udzial w tworzeniu standardu/RFC, itp, to moznaby by dyskutowac